Acetabular cup remover with indexing assembly for rotating the removal blade around the cup

ABSTRACT

An acetabular cup remover with a blade for removing tissue adjacent an acetabular cup. The blade is oscillated against an arcuate section of tissue. Once a section of tissue is cut, an indexing assembly rotates the blade. The blade is again oscillated to cut a new arcuate section of tissue.

RELATIONSHIP TO EARLIER FILED APPLICATION

This application is a continuation of PCT Pat. App. No.PCT/US2013/028535 filed 1 Mar. 2013 now expired. The contents of theabove-identified priority application are explicitly incorporated hereinby reference.

FIELD OF THE INVENTION

This invention relates generally to an acetabular cup remover. Moreparticularly, the acetabular cup remover of this invention is able torotate cup removable blade around the cup being removed.

BACKGROUND OF THE INVENTION

One area of the body which is highly prone to chronic pain anddegeneration of normal function is the hip joint. Whether caused bydisease, aging, overuse, or injury, a portion of the population suffersfrom ailments relating to the hip. An often utilized solution toproblems pertaining to the hip joint is total hip replacement (“THR”)surgery. Generally, THR surgery consists of the replacement of theexisting ball and socket of the hip joint with prosthetic replacements.The head of the femur (i.e. —the ball) is typically removed and replacedwith a femoral component made of biocompatible material, which mirrorsthe structure of the original bone. The acetabulum (i.e. —the socket) istypically reamed and fitted with a prosthetic acetabular cup componentthat corresponds and cooperates with the femoral component. Thisprosthetic acetabular cup component often times includes an outer shellconstructed of a metallic material. Typically this shell is in the formof a hollowed out semi-sphere. An insert constructed of plastic, ceramicor metal received within the outer shell. In many cases, the acetabularcup component is anchored in the bone through the use of cement. Somecups are press fit in place. Still other cups are held in place byscrews or fastening tabs integral with the cup itself. A combination ofthese fastening methods may be employed. Sometimes owing to the shape ofthe outer shell and/or the application of compound that enhance bonegrowth, the outer shell is designed to foster the growth of boneadjacent the shell. This new bone anchors the cup to the rest of thehip. Total hip replacement surgery has often proven successful inrelieving many problems associated with the hip joint.

Even though total hip replacement surgery is often successful, it issometimes necessary to perform the same surgery on the same hip. Thismay be necessary in situations in which wear or infection degrade theperformance of the installed cup and femoral head. This sub-set of totalhip replacement surgery is sometimes called revision surgery. Inrevision surgeries, it is necessary to remove the acetabular componentpreviously implanted in the acetabulum. As mentioned above, thesecomponents may have been cemented in place or otherwise held by bone orfibrous tissue that may have grown in and around the component. Thus,their removal requires the cutting or chipping away of cement or bonematerial.

The Inventor's Assignee's U.S. Pat. No. 8,034,059, ACETABULAR SHELLREMOVAL INSTRUMENT, issued 11 Oct. 2011, the contents of which areexplicitly incorporated herein by reference, discloses a surgical tool,acetabular cup remover, designed to perform a revision process. As itsname implies, this tool is designed to remove an already implantedacetabular cup. This tool includes a head that is dimensioned to seat inand rotate in an implanted acetabular cup. Plural shafts extend awayfrom this head. A blade is pivotally mounted to one of these shafts. Theblade curves forward such that the blade curves around the head. One ofthe shafts is able to move longitudinally relative to the head. Theblade is connected to this first shaft to pivot as a function of thelongitudinal movement of the shaft. A second shaft is rigidly connectedto the head. The blade is connected to this second shaft. Axial rotationof this second shaft results in a rotational movement of the bladearound an arc. The second shaft is connected to a power tool thatoscillates the shaft.

This tool is used by seating the head in the cup that is to be removed.The first shaft is pressed downwardly. This results in the pivoting ofthe blade against the bone in adjacent the cup. The power tool isactuated. Thus simultaneously the blade is pressed against bone andoscillated in an arc around the cup. The blade cuts the bone adjacentthe cup. The tool is indexed and the blade pivoted so that the bladeforms a cut that extend completely around the portion of the cupembedded in the bone. The formation of this cut separates the cup fromthe bone in which the cup is embedded. The cup can then be removed and anew one installed.

The above-described acetabular cup remover can be a useful tool forremoving an acetabular cup. There is, however, an inefficiencyassociated with this tool. When the tool is used, the blade is typicallyoscillated around an arc that of 15° or less and more often 10° or less.Once one section of the cut is formed, the tool must be rotated so theblade can be positioned to cut an adjacent section of the cut. To formthe cut it is necessary to rotate the power tool to which the cupremover is attached. This results in the centering of the blade over theportion of the bone in which the new section of the cut is to be formed.This requires the surgeon forming the cut to reposition how the powertool is held. Having to so reposition the tool may require the surgeonto hold the power tool in positions that, ergonomically, can impose astrain. Further, having to so reposition the handpiece can add to thetime it takes to perform the revision surgical procedure. Having toperform these steps runs counter to one of the primary goals whenperforming surgery, that one should perform the procedure as quickly aspossible to both minimize the likelihood the exposed tissue is open toinfection and the amount of time the patient is held under anesthesia.

SUMMARY OF THE INVENTION

This invention is directed to a new and useful acetabular cup removerfor use in a revision hip replacement procedure. The acetabular cupremover of this invention has features designed to substantially, if notcompletely, eliminate the need for a surgeon performing the procedure tohave to index the tool used to oscillate the blade.

The cup remover of this invention includes a head. The head is shaped toseat in the cup the remover is intended to remove. A shaft extendsproximally away from the head. A blade is pivotally attached to theshaft. Attached to the shaft is an assembly that allows the surgeon toselectively pivot the blade so the blade can be driven forward of thecup. The shaft is attached to a power tool known as a driver. The driversupplies power that oscillates the shaft. Between the driver and theblade is an indexing assembly. The indexing assembly allows the surgeonto set the rotational orientation of the blade assembly relative to astatic axis that extends along the shaft without having to disconnectthe blade from the tool.

In some, but not all, versions of the invention, the blade and assemblythat pivots the blade is attached to the shaft. The indexing assemblyindexes the shaft and, by extension, the blade assembly.

The surgical tool, the cup remover, of this invention is used by firstseating the head against the inner surface of the cup that is to beremoved. The surgeon displaces the blade to force the blade against asection of the bone immediately adjacent the cup. The driver is actuatedto oscillate the shaft. The oscillation of the shaft results in a likeoscillation of the blade. The blade is thus forced against the bone toform an arcuate cut in the bone around the cup.

Once an arcuate cut is formed in the bone, the surgeon uses the indexingassembly to reset the rotational orientation of the blade assemblyrelative to a longitudinal axis that extends through the shaft. Again,in some but not all versions of the invention, this indexing isperformed by rotating the shaft. Thus, by using the indexing assemblythe surgeon is able to set the blade over the next arcuate section ofbone in which the cut is to be formed. The surgeon is to perform thistask without having to either completely disconnect the shaft from thetool or having to reset the rotational orientation of the driverrelative to the cup.

In some versions of this invention there is a transmission. Thetransmission converts the rotary motion of a shaft integral with thedriver into a motion that oscillates the shaft of the cup remover. Insome embodiments of the invention parts of the transmission alsofunction as parts of the indexing assembly that rotates the shaft. Inother versions of the invention the indexing assembly and thetransmission consist of essentially separate components.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features and benefits of this invention are understood bythe following Detailed Description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a perspective view of an acetabular cup remover of thisinvention;

FIG. 2 is an assembly diagram depicted how FIGS. 2A and 2B are assembledtogether to form an exploded view of the components of this invention;

FIG. 3 is a plan view looking into the distal end of the driver;

FIG. 4 is a perspective view of the motor shaft internal to the driver;

FIG. 5 is a cross sectional view of the transmission components andcoupling components attached to the driver;

FIG. 6 is a perspective view of the cup insert fitted to the driver;

FIG. 7 is a cross sectional view of the cup insert;

FIG. 8 is a perspective view of the eccentric housing;

FIG. 9 is a plan view of the proximal end of the eccentric housing;

FIG. 10 is a cross sectional view of the eccentric housing taken alongline 10-10 of FIG. 9;

FIG. 11 is a perspective view of an eccentric shaft;

FIG. 12 is a perspective view of the eccentric shaft and bearingassemblies fitted over the shaft;

FIG. 13 is a cross sectional view of the sub assembly of FIG. 12

FIG. 14 is a perspective view of the link

FIG. 15 is a plan view of the link;

FIG. 16 is a perspective view of the output spindle of the driver;

FIG. 17 is a cross sectional view of the output spindle taken along line17-17 of FIG. 16;

FIG. 18 is a cross sectional view of the output spindle taken along line18-18 of FIG. 16;

FIG. 19 is a perspective view of a spacer internal to the eccentrichousing;

FIG. 20 is a cross sectional view of the spacer of FIG. 19;

FIG. 21 is a perspective view of the lock cap;

FIG. 22 is a cross sectional view of the lock cap;

FIG. 23 is a perspective view of the retainer associated with thedriver;

FIG. 24 is a plan view of the retainer when viewed from the top;

FIG. 25 is a cross sectional view of the retainer;

FIG. 26 is plan view of the shaft of the cup remover;

FIG. 27 is a perspective view of the input spindle of the cup remover;

FIG. 28 is a cross sectional view of the input spindle;

FIG. 29 is a perspective view of the handle of the cup remover;

FIG. 30 is a cross sectional view of the handle of FIG. 29;

FIG. 31 is a cross sectional view of the handle depicting the componentsin the handle;

FIG. 32 is a perspective view of the head-to-shaft coupler between theshaft and the pivot head;

FIG. 33 is a side plan view of the coupler of FIG. 32;

FIG. 34 is a perspective view of the pivot head;

FIG. 35 is a perspective view of the blade;

FIG. 36 is a perspective view of the hinge;

FIG. 37 is an assembly view of the components attached to the hinge thatreleasably hold the blade to the hinge;

FIG. 38 is a plan view of the actuator rod;

FIG. 39 depicts the lock collar disposed in the handle;

FIG. 40 depicts the actuator; and

FIG. 41 is a cross sectional of how the cup remover is removablyattached to the driver.

DETAILED DESCRIPTION I. Overview

FIG. 1 illustrates a surgical tool, acetabular cup remover 30, of thisinvention and the relation of the tool to an acetabular cup 32. The cup32 is often in the form of a hollow semi-spherical structure typicallyformed of metal. The outer surface of the cup 32 is embedded in bone ofthe hip. The inner surface of the cup defines a socket. This socket wasdesigned to receive the ball of a femoral stem. While not illustrated, aliner, often in the form of a hollow semi-spherical structure, may beseated against the inner surface of the cup 32. A liner, when present,defines the socket space that receives the femoral ball.

The cup remover 30 includes a pivot head 388. Head 388 is the portion ofthe cup remover 30 that is seated in the cup 32. A shaft 292 extendsproximally from the head 388. (“Proximally,” it is understood meanstowards the surgeon using the cup remover 30, away from the cup 32.“Distally” means away from the surgeon, towards the cup 32.) A blade 402is pivotally attached to shaft 292 a short distance proximally rearwardfrom the head. Blade 402 has an arcuate profile and is positioned so asto curve distally forward and around the head 388. More particularly,the blade 402 is shaped so that when the head 388 is seated in the cup32 the blade, when pivoted distally forward, advances around the outersurface of the cup.

A hinge 418 is connected to shaft 292. Hinge 418 pivots the blade arounda pivot axis so as to advance and retract the blade relative to thedistal end of head 388. This pivot axis is understood to be in a staticlocation relative to shaft 292. A handle 332 is slidably connected tothe shaft 292. The handle 332 is connected to hinge 418 to pivot thehinge. Thus the handle 332 and hinge 418 can collectively be considereda blade pivoting assembly.

Cup remover 30 is actuated by a power tool, referred to as a driver 50.Driver 50 includes a motor 68. A coupling assembly 280 releasableconnects the tool 30, namely the shaft 292 and handle 332, to driver 50.A transmission assembly 89 converts the rotational movement of a shaft70 (FIG. 4) integral with the motor 68 into an oscillatory motion. Thismotion is transmitted by the coupling assembly to the cup remover shaft292 as oscillatory motion. The oscillation of shaft 292 results in alike oscillation of the cup remover blade 402.

The driver transmission 89 and coupling assembly 280 also collectivelyform an indexing assembly 95. This indexing assembly allows the surgeon,by rotating handle 332, to set the rotational orientation of the cupremover shaft 292 around an axis that extends longitudinally through theshaft 292. The indexing of cup remover shaft 292 results in a likesetting of the rotational orientation of blade 402 relative to cup 32.

II. Driver

One powered driver 50 that can be employed with cup remover 30 is nowdescribed with respect to FIGS. 1, 2B and 3. Driver 50 includes ahousing 52. In the particular version of the invention, housing 52 isshaped to have a barrel 54 that forms the head of the housing. Thehousing 52 is further formed so as to have a bore 56 that extendsinwardly from the distally directed face of barrel 54. The cylindricalinner wall of housing 52 that defines bore 56 is formed with threading58. The threading 58 is locating in the section of the wall immediatelyproximal to the distal open end of bore 56. Internal to housing is a web53. Web 53 defines the proximal end of bore 56. The web 53 is formedwith a center opening 55 and a pair of notches 57 located on the opposedsides of the opening. A pistol-grip shaped handle 62, also part of thehousing 52, extends downwardly from head 54.

A motor 68, represented by a phantom cylinder, is disposed insidehousing barrel 54. In some versions of the invention, the motor 68 is abrushless DC motor. It should be appreciated that this is exemplary, notlimiting. In other versions of the invention, the motor may be a DCmotor with brushes, an AC driven motor or a motor that is pneumaticallyor hydraulically driven. Motor 68 includes a rotating shaft 70. As seenin FIG. 5 motor shaft 70 includes a cylindrical stem 72. In versions ofthe invention in which the motor 68 is an electric motor, the stem 72 isthe portion of the motor disposed in the motor stator. A head 74 formsthe distalmost section of the shaft 70. The head 74 is cylindrical andcoaxial with the stem 72. The head 74 is formed to have gear teeth 76.Driver 50 is assembled so that the casing of the motor (casing notidentified seats in web opening 55. As a consequence of this positioningof the motor 68, the shaft head 74 is disposed in the proximal end ofdriver housing bore 56. Not described and not part of this invention arethe structural components of the driver 50 that protect the componentsof the motor 68 not disposed in bore 56 from the adverse affects ofautoclave sterilization.

In the illustrated version of the invention, driver 50 is a cordlesstool. A battery 80, seen only in FIG. 3, is removably attached to thebutt end of the handle 62 contains a charge for energizing the motor.Again, it should be understood that the invention is not so limited. Inalternative versions of the invention, a power cord, an air line or afluid line may be connected to the handpiece for providing the powerneeded to actuate the motor.

A trigger 84 is moveably mounted to the driver housing 52. In theillustrated version of the invention, trigger 84 extends distallyforward from the handle 66 immediately below the barrel 54. A controlcircuit internal to the handle 66, not illustrated and not part of thisinvention, monitors the actuation of the trigger 84. Based on the extentto which the trigger switch 84 is actuated, the control circuitselectively energizes the motor 68 to cause an shaft 70 to rotate at thedesired speed.

As seen by FIGS. 2B and 5, a number of components of the transmissionassembly 89 are mounted in the driver housing bore 56. One of thesecomponents is a generally cylindrical cup insert 92 now described byreference to FIGS. 6 and 7. The cup insert 90 is formed from a singlepiece of material typically hardened steel. Cup insert 92 is shaped tohave generally tube shaped main body 93. The outer diameter of the mainbody 93 is dimensioned to closely slip fit in drive housing bore 56. Aring shaped base 94 extends proximally from body 93. Base 97 has innerand outer diameters slightly less than those of body 93. Two feet 98project proximally away from the proximal end of base 94. Feet 98 arediametrically opposed to each other around the longitudinal axis thatextends through the cup insert. Feet 98 are dimensioned to, when thedriver 50 is assembly closely seat in driver notches 57.

Cup insert 92 is further formed to have adjacent the proximal end twoflats 102. Flats 102 extend distally from the proximal end of the mainbody 93. Each flat 102 is, relative to the longitudinal axis of the cupinsert 90, spaced from the adjacent teeth 98. Flats 102 are not part ofthe present invention.

An eccentric housing 108, seen best in FIGS. 8-10, is rotatably seatedin cup insert 92. Eccentric housing is formed is a single piececomponent typically formed from hardened steel. Eccentric housing 108 isformed to have a base 110 and a stem 112, both of which are cylindricalin shape. The base 110 has an outer diameter greater than that of stem112. Base 110 has a diameter that allows the base to closely slip fitand rotate in the void space with the cup insert main body 93. Theproximal end of the base is solid. Two parallel bores 116 extendslongitudinally through the solid portion of the base 110. Bores 116extend from the proximal end of the base 110. The bores 116 arediametrically opposed to each other relative to the longitudinal axisthrough the eccentric housing 108. The eccentric housing 108 is furtherformed so an annular groove 118 extends outwardly from each of theinterior cylindrical walls of the housing that define a separate one ofthe bores 116. Each groove 118 protrudes outwardly from the bore 116 ata location that is slightly forward from the proximal ends of the bores.

The eccentric housing 108 is further formed so that there a recess 120extends inwardly from the proximal face of the housing. Recess 120defines a circle that is centered on the longitudinal axis through thehousing 108. Recess has an outer diameter that allows the head 74 of themotor shaft 70 to seat in the recess. It should thus be appreciated thatthe recess 120 intersects the open proximal ends of bores 116.

The proximal ends of bores 116 open into a common bore 124. Bore 124 isformed in the distal portion of the eccentric base 110. Bore 124 iscylindrical in shape and coaxial with the longitudinal axis through theeccentric housing 108. The proximal end of bore 124 opens into a coaxialcylindrical bore 128. Bore 128 is formed in the housing stem 112. Bore128 extends to the distal end of the eccentric housing 108. Eccentrichousing 108 is further formed to have an interior located ring shapedledge 126. Ledge 126 is located at the step between the housing base 110and stem 112. Ledge thus defines a small disc like space (notidentified) within the housing 108 between bore 124 and bore 128.

Eccentric housing 108 is further formed to have two diametricallyopposed openings 130. Each opening 130 extends laterally through thehousing stem 112 into bore 128.

An eccentric shaft 136, seen in FIG. 11, is rotatably disposed in eachbore 116 of the eccentric housing 108. Each eccentric shaft includes acylindrical foot 138. The foot 138 is formed with teeth (not identified)dimensioned to engage the teeth 76 of motor shaft 70. A cylindrical leg140 extends distally from the foot 138. Leg 140 extends to a ring shapedcollar 142. Collar 142 is coaxial with foot 138 and leg 140 and has agreater outer diameter than the leg 140. A cylindrical head 146 extendsdistally forward from collar 142. The longitudinal axis of head 146 isparallel with and laterally offset from the common longitudinal axisthrough shaft foot 138, leg 140 and collar 142. Immediately proximal tothe distal end of the head 146, the eccentric shaft 136 is formed tohave an annular groove 148 that extends circumferentially around theouter surface of the head.

In some versions of the invention, for ease of manufacture, foot 138 isformed as a separate component. A stem (not identified) extends upwardlyfrom the foot. The shaft leg is formed with a bore (not identified) thatis that extends distally from the proximal end of the leg. The stemintegral with the foot 138 is press fit into the bore internal to theleg 140.

Two bearing assemblies 152 and 158, seen best in FIGS. 12 and 13,rotatably hold each eccentric shaft 136 in the eccentric housing bore116 in which the shaft is seated. While not depicted, it should beunderstood that each bearing assembly includes inner and outer races anda set of ball bearings between the races. The inner races of the bearingassemblies 152 and 158 are dimensioned to press fit over the adjacentshaft leg 140. The outer races of the bearing assemblies 152 and 158 aredimensioned to tightly fit in the bore 116 in which the assemblies areseated. Bearing assembly 152 is the proximal of the two bearingassemblies. Bearing assembly 152 is positioned on shaft 136 so that theinner race of the assembly is located immediately forward of theproximal end of shaft leg 140. A snap ring 150, the purpose of which isdiscussed below, is sandwiched between the foot 138 and the proximal endof the leg 140.

Bearing assembly 158 is located forward of bearing assembly 152. In theillustrated version of the invention, bearing assembly 158 is longer inlength than bearing assembly 152. The inner race of bearing assembly 158is seated against the proximally facing surface of shaft collar 142 thatextends radially outwardly of shaft leg 140.

Each eccentric shaft 136 and associated bearing assemblies 152 and 158are seated in the eccentric housing 108 so that the outer races ofbearing assemblies seat against the inner cylindrical wall of thehousing that defines a bore 116. Snap ring 150 is disposed in the groove118 contiguous with the bore 116. The proximally directed face of theouter race of bearing assembly 152 seats against the adjacent exposedface of the snap ring 150. The snap ring 150 thus holds the shaft andbearing assemblies 152 and 158 in the bore 116. A spacer 156 is disposedbetween the adjacent linearly aligned bearing assemblies 152 and 158.Spacer 156 is a ring formed from metal or plastic. The components ofthis invention are selected such that the outer surface of the spacer156 is disposed against the adjacent bore 116 defining wall. Forwardmovement of the shaft 136 and bearing assemblies 152 and 158 is blockedby the abutment of the distally directed surface of the outer race ofbearing assembly 158 against the adjacent proximally directed face ofthe ledge 123 internal to the eccentric housing.

Upon the mounting of the eccentric shafts 136 to the eccentric housing108, the shaft feet 136 extend partially out the proximal end of thehousing. The shaft heads 146 are disposed in the bore 124 internal tothe housing 108. A bearing assembly 162 is disposed over each shaft head146. Bearing assemblies 162 each include an inner and outer race (notillustrated. The inner race is tightly fit of the shaft head 144. A snapring 164 disposed in groove 148 that extends inwardly from shaft head148. The snap ring 164 extends over the inner race of the adjacentbearing assembly 162 so as to hold the bearing assembly to the shafthead 146.

When driver 50 is assembled, the eccentric housing 108 with componentsdisposed therein is seated in the cup insert 92. More particularly, theproximal portion of the eccentric housing base 110 is disposed againstthe inner cylindrical wall of the cup insert main body 93. The proximalend of eccentric housing 108 is disposed against the distally directedface of cup inset base 94. The toothed feet 138 of the eccentric shafts136 are located adjacent and engage the teeth 76 integral with the drivemotor shaft. There is a close slip fit between the cup insert 92 and theeccentric housing. Owing to the dimensioning of these components and thematerial from which they are formed, the eccentric housing 108 is ableto rotate within the cup insert 92. By extension, the eccentric housing108 is able to rotate around the extension of an axial line that extendsout of the drive housing barrel 54.

A link 168, now described by reference to FIGS. 14 and 15, is alsodisposed in eccentric housing 108. Link 168 is a single piece componentformed from hardened steel. The link 168 is shaped to have two planar,rectangularly shaped plates 170. Plates 170 are parallel and spacedapart so that the plates can closely fit over bearing assemblies 162.The plates 170 extend distally forward to a common web 172. Web 172 isplanar in shape and has a perimeter that is generally oval. Acylindrical head 176 extends distally forward from face of web 172opposite the face from which plates 170 extend. The head 176 extendsoutwardly from the center of web 172. Immediately adjacent the web 172 acollar 174 extends around the proximal end of head 176. The collar 174projects radially outwardly beyond the outer surface of head 176.

Link 168 is further formed to have a nose 178 that extends from thedistal end of the head 176. Nose 178 is stepped inwardly from the outerperimeter of head 176. The nose is shaped to have two flat outersurfaces (not identified). These surfaces are parallel to each other andto plates 170. A curved surface (not identified) extends between eachpair of opposed ends of the ends of the flat surfaces. A bore 180extends proximally inward from the distal end of nose 178. The internalwall internal to the link nose 176 that defines bore 180 is formed withthreading (not illustrated). Nose 178 and bore 180 are coaxial with linkhead 176.

An output spindle 184, now described by reference to FIGS. 16-18,extends forward from link 168. The output spindle 184 is formed as asingle component and formed out of metal such as hardened steel. Theoutput spindle 168 is formed to have cylindrical foot 186. Foot 186 hasan outer diameter equal to the diameter of link head 176. A cylindricalleg 188 is coaxial with foot 186 and extends distally forward of thefoot. Leg 188 has an outer diameter greater than that of the foot 186.Forward of leg 188, the output spindle 184 has a circular head 190. Head192 extends radially outwardly from leg 188. Head 190 is coaxial withfoot 186 and leg 188. Two ears 194 project forward from head 190. Eachear 194 is in the form of a slice section of the circle subtended byhead. The ears 194 are spaced apart from each other so as to define anannular notch 196 therebetween. Notch 196 extends diametrically acrossthe output spindle. The distally directed face of the head 192 forms thebase of notch 196.

Output spindle 184 is further shaped so as to have a bore 198 thatextends forward from the proximal end of the spindle foot 186. Bore 198,as seen in FIG. 18, has what is referred to as a double-D shape. Moreparticularly, the bore 198 is shaped to closely receive link nose 178.Bore 198 extends approximately one-half way through spindle foot 186.Bore 198 opens into a cylindrical bore 204. Bore 204 is coaxial withbore 198 and extends through the distal portion of foot 186, leg 188,neck 190 and head 192. A step 199, is the transition surface internal tothe spindle foot 186 between bore 202 and bore 204. Bore 204 opens intothe exposed face of the head 190, the surface of the head that definesthe base of notch 196.

Spindle leg 188 is formed to have two diametrically opposed openings201. Openings 201 open into bore 204. Each opening 201 is the form istapered such that the narrow diameter portion of the opening forms theinlet into the bore 204. A ball bearing 205 is seated in each opening201. When the ball bearing 205 is fully seated in the associated opening201, a portion of the bearing protrudes into spindle bore 204.

The foot 188 of output spindle 184 is seated over the nose 178 integralwith link 168, as seen in FIGS. 2B and 5. The link nose 178 extends intobore 198 internal to the output spindle 184. A washer 182, identifiedonly in FIG. 2B, is seated over the step 199 internal to the outputspindle 184. A threaded fastener 206, identified only in FIG. 2B, isseated in the spindle bores 198 and 204. Fastener 206 is threaded intobore 180 internal link 168. The head of fastener 206 seats againstwasher 182.

Bearing assemblies 210 and 216 rotatably hold link 168 and outputspindle 184 in eccentric housing bore 128. While not seen, it isunderstood both bearing assemblies 210 and 216 include inner and outerraces. The outer races of both bearing assemblies 210 and 216 aredisposed against the surface internal to the eccentric housing stem 112that defines bore 128. The inner race of the proximalmost bearingassembly, assembly 210, is seated over link head 176. The proximal endof the inner race of bearing assembly 210 is disposed against thedistally directed face of the link collar 174.

A spacer 213 disposed within eccentric housing bore 128 holds bearingassembly 216 distally away from bearing assembly 210. Spacer 213 isformed from aluminum and is tube shaped, as seen in FIGS. 19 and 20.Spacer 213 has an outer diameter that facilitates the non rotationalfitting of the spacer against the inner cylindrical wall of housing stem112. The inner diameter of the spacer 213 is such that there is aclearance between the spacer and the link head 176 and output spindlefoot 186 that are disposed within the spacer. The spacer is formed withtwo pairs of diametrically opposed threaded openings 214. The pairs ofthe openings are symmetric relative to a lateral plane that bisects thespacer. Each opening 214 open into the center void of the spacer 213. Aswill be apparent below this invention requires only a single pair ofopenings 214. The second pair of openings is provided for ease ofassembly.

When the driver 50 is assembled, the proximally directed face of spacer213 rests against the adjacent face of the outer race of bearingassembly 210. The proximally directed of the outer race of bearingassembly 216 seats against the adjacent distally directed face of spacer213. The inner race of bearing assembly 216 is disposed around the foot186 of the output spindle 184. The distal end of the inner race ofbearing assembly 216 is located adjacent the step that defines thetransition between spindle foot 186 and leg 188, step not identified. Inthe depicted version of the invention, a washer 218, identified only inFIG. 2B, is sandwiched between the bearing assembly 216 and the step.Upon assembly of the driver, leg 188, head 190 and ears 194 of theoutput spindle 184 are located forward of the eccentric housing 108.

A lock cap 222, best seen in FIGS. 21 and 22 holds the eccentric housing108 and the components disposed therein to the driver 50. The lock cap222 is generally in the form of a tube. The proximal end of the tubeportion of the lock cap is provided with threading 224 around the outersurface, threading seen only in FIG. 21. More specifically, this portionof the lock cap 222 is designed to seat in housing bore 56 so the capthreading 224 can engage the driver housing threading 58. The distalportion of the lock cap is formed to have an outer surface thatextending distally along the cap, tapers inwardly. Proximal to theinwardly tapered surface, the cap 222 is formed to have a number ofclosed end bores 226. Bores 226 are provided to receive a tool (notillustrated) able to rotate the cap 168.

Owing to the tube like shape, the inside of the lock cap 222 is a voidspace 228. The cap is further formed to have two annular lips 230 and232 that extend inwardly from the inner wall of the cap into this voidspace. The proximalmost of these lips, lip 230, is located less than 0.5cm from the distal end of the cap. The distalmost lip, lip 232, extendsinwardly from the distal end of the cap 222. Relative to thelongitudinal axis through the lock cap 222, lips 230 and 232 are spacedapart from each other.

When the driver 50 is assembled, the eccentric housing 108 andcomponents seated in the housing are fitted in drive housing bore 56.Lock cap 222 is screw secured in bore 56. The proximal movement of thelock cap 222 into the housing barrel 54 is limited by the abutment ofthe proximal end of the cap against the adjacent distal end of the cupinsert 92. The components of this invention are dimensioned so the outersurface of the eccentric housing base 108 is spaced inwardly from thesurrounding inner surface of the lock cap 222. Lock cap lip 230 extendsover the stepped surface of the eccentric housing that separates thebase 110 from the stem 112. This arrangement holds the eccentric housing108 for rotation to driver housing barrel 54. Eccentric housing stem 112extends forward of the lock cap 222.

As part of the assembly process an O-ring 231 is seated between lock caplips 230 and 232. The O-ring 231, identified in FIGS. 2B and 5, providesa seal between the eccentric housing 108 and the lock cap 222.

A retainer 236, initially described by reference to FIGS. 23-25, isdisposed over both the distal portion of the eccentric housing 108 andthe portion of the output spindle 184 that extends forward of thehousing. The retainer 236 is formed as a single piece unit and has aring shaped skirt 238 that forms the proximal portion of the retainer.Two diametrically opposed slots 240 extend forward from the proximal endof the skirt 238. In the depicted version of the invention, the slots240 are U-shaped. A tube shaped collar 242 is integral with and extendsdistally forward from skirt 238. Collar 242 has an outer diameter lessthan that of skirt 238. Two diametrically opposed ribs 244 projectoutwardly from the distal end of collar 242. Each rib 244 islongitudinally aligned with a separate one of the slots 240 Each rib 244extends proximally so as to terminate at the step between the skirt 238and collar 240, (step not identified). A ring like neck 245 extendsdistally forward from collar 240. Neck 245 has an outer diameter lessthan that of the adjacent collar 242.

Retainer 236 is formed to have a number of void spaces. One of thesevoid spaces is a bore 248. Bore 248 extends forward from the proximalend of the skirt 238. The bore 248 extends longitudinally through thewhole of the skirt 238 and an adjacent proximal portion of collar 240.The retainer 236 is dimensioned so that bore 248 can receive in slidingengagement stem 112 of eccentric housing 108. Slots 240 open into bore236. Four bores, all coaxial with bore 248, extend distally from bore236 to the distal end of retainer neck 242. Bore 250 is the boreimmediately distal to and contiguous with bore 248. Bore 250 has adiameter less than that of bore 248. Bore 250 opens into a bore 252.Bore 252 has a diameter less than that of bore 250. Bore 252 also opensinto an annular groove 254 also disposed within retainer collar 240.Groove 254 is radially spaced from and extends around the proximalportion of bore 252. The outer diameter of groove 252 is equal to thediameter of bore 250.

Bore 256 is the bore that is immediately distal to and contiguous withbore 252. Bore 256 has a diameter greater than that of bore 252. Likebore 252, bore 256 is disposed wholly within retainer collar 240. Bore256 opens into bore 258, the distalmost of the retainer bores. Bore 258has a diameter greater than that of bore 256. More particularly bore 258has a diameter that allows the slip fitting of the output spindle head192 and ears 194 in the bore 258. Bore 258 extends through the distalend of the retainer collar 240 and through the whole of retainer neck242.

Retainer 236 is formed to have two additional bores, bores 260. Eachbore 260 is a closed end bore formed in one of the ribs 230. Each bore260 extends from the distally directed face of the rib 230 in which thebore is located. Bores 260 are parallel to the proximal-to-distallongitudinal axis through the retainer 222. A cylindrical pin 262, seenin FIGS. 2B and 5, is press fit in each bore 260. Pins 262 extendforward from retainer 236.

When driver 50 is assembled, two screws 264, seen in FIGS. 2B and 5, arefitted to the eccentric housing 108. Each screw 264 is seated in one ofthe openings 130 in the housing stem 112. The shaft of each screw isthreaded into the spacer opening 214 in registration with the eccentrichousing opening 130. Retainer 236 is slip fitted over the eccentrichousing stem 112 so that the head of each screw 264 seats in a separateone of the retainer slots 240. A coil spring 266 is placed in front ofbearing assembly 216. The output spindle 184 is secured to link 168 withfastener 206.

As a consequence of the mating of the output spindle 184 to the rest ofthe driver 50, the spindle neck 192 and head 194 seat, respectively, inretainer bore 256 and bore 258. The distal end of the spring 266 seatsin the annular surface internal to the retainer 236 that defines groove254. Spring 266 exerts a force on the retainer 236 that pushes theretainer distally away from the eccentric housing 108. The distalmovement of the retainer 236 is limited by the abutment of the annularwalls internal to the retain that define the transition from bore 256 tobore 258 to the adjacent faces of the output spindle that define thetransition from the spindle neck 192 to the spindle head 194. When theretainer 236 is so positioned, the section of the spindle leg 188 thatdefines the openings 201 is surrounded by the ring like internal sectionof the retainer 236 that separates bore 252 from groove 254. Thissection of the retainer 236 thus blocks the outward movement of the ballbearings 205 out of spindle openings 201. It should further beappreciated that, upon assembly of the driver 50, pins 262 extendforward of the output spindle 184 and form the distalmost components ofthe driver 50.

The components of the driver 50 internal to the eccentric housing 108form the transmission components that convert the rotary motion ofdriver shaft 70 into an oscillatory motion. The output spindle 184,bearings 205, retainer 236 and spring 266 form the driver portion of thecoupling assembly 280 that removably hold the cup remover 30 to thedriver 50. As discussed below these components also form part of theblade indexing assembly 95.

III. Cup Remover

Shaft 292, now described with reference to FIG. 26 is one of thecomponents of the cup remover 30 that transfers the rotational andoscillatory movement of driver link 168 to the blade 402. Shaft 292 isgenerally in the form of an elongated rod. At the proximal end, shaft292 has a cylindrical stem 294. A bore 296 extends laterally through thestem 294. Proximal to stem 294, the shaft 292 has a trunk 298. Trunk 298is generally cylindrical in shape and has a diameter greater than thatof the stem 294. Trunk 298 is further formed to a longitudinallyextending groove 302. Groove 302 extends distally forward from alocation approximately one-half way along the length of the trunk.Groove 302 is concave in shape. The groove 302 extends forward to andopens above a flat 304 formed in the trunk 298. Generally speaking, theshaft 292 is formed so that the curved section of the trunk that definesthe flat 304 subtends an angle of at least 180° around the longitudinalaxis of the shaft.

Forward of trunk 298, the shaft 292 has a cylindrical head 306. Head 306is coaxial with the stem 294 and trunk 298. The head 306 thus has asection that extends above flat 304. In the depicted version of theinvention, head 306 has a smaller diameter then the diameter of thetrunk 298. A bore 307 extends laterally through the head 304.

An input spindle 312, seen best in FIGS. 27 and 28, releasably connectsshaft 292 to the driver 50. Spindle 312 includes a cylindrical base 314.A circular collar 316 extends proximally from base 314. Collar 316 hasan outer diameter that is greater than that of base 314. Morespecifically, the outer diameter of collar 316 is equal to the diameterof the circle defined by ears 194 integral with the output spindle 184integral with driver 50. A neck 318 projects outwardly from the exposedface of collar 316. The neck 318 is in the form of a bar that extendsdiametrically across the face of collar 316. The minor surfaces of thebar forming neck are curved so as to be flush with the outer perimeterof the collar 316. The side-to-side width across the neck 318 is suchthat the neck can be close slip fitted in notch 196 formed by the outputspindle 184.

Input spindle 312 is further formed so that a generally cylindrical head318 extends proximally away from neck 318. Head 318 is coaxial with base314 and collar 316. The head 318 has a diameter that allows the head tobe closely slip fitted into bore 204 internal to the output spindle 184.The input spindle 312 is further formed so that an annular groove 320extends circumferentially around head 318. Groove 320 is arcuate incross section. The input spindle 312 is shaped so that when the spindlehead 318 seats in output spindle bore 204, ball bearings 205 will seatin groove 320.

The input spindle 312 is further formed so as to have a bore 322 thatextends proximally from the distally directed face of spindle base 314.Bore 322 is dimensioned to press fit receive shaft stem 294. The base314 is further formed to have two coaxial openings 324. Openings 324each open into bore 322.

When the cup remover 30 is assembled, the input spindle base 312 ispress fit over shaft stem 294. A pin 326, seen only in FIGS. 2B and 41,extends through spindle openings 324 and shaft bore 296 to further holdthe shaft 292 and input spindle 312 together.

Handle 332, now described by reference to FIGS. 29 and 30, is slidablydisposed over both the proximal portion of shaft 292 and the base 314 ofthe input spindle 312. The handle 332 is a single piece component that,like essentially all components forming the cup remover 30, can besubjected to autoclave sterilization. The handle 332 is generally in theform of a tube. The handle is shaped to have a head 334 that has agenerally constant outer diameter. Head 334 is the most proximallylocated portion of the handle 332. A trunk 336 extends distally fromhead 334. The trunk has a varying outer diameter. Specifically, thetrunk is shaped to ergonomically receive the palm of the hand andfingers of the individual using cup remover 30. A base 338 forms thedistalmost portion of handle 332. The base 338 has a constant outerdiameter. In the illustrated version of the invention, the diameter ofbase 338 is less than that of head 334.

A set of bores extend axially through the handle 332. A first bore, bore342, extends distally forward from the proximally directed face of thehead 334. Bore 342 extends partially through the head 334. Bore 342 isdimensioned to slidingly receive the base 314 of the input spindle 312.Bore 342 opens up into a bore 344. Bore 344 extends through the distalportion of the head 334 and most of the trunk 336. Bore 344 has adiameter less than that of bore 342. The bore 344 is dimensioned toslidably receive shaft 292. Adjacent bore 342 a groove 346 extendsoutwardly from the cylindrical inner wall of handle 332 that definesbore 344. The distal end of bore 344 opens into a bore 348. Bore 348extends through the most distal portion of the trunk and the adjacentproximal section of the base 338. Bore 348 has a diameter greater thanthat of bore 344. Bore 348 opens into a bore 350 which is the distalmostbore of the handle 332. Bore 350 extends from bore 348 to the distallydirected face of the handle 332. Bore 350 has a diameter greater thanthat of bore 348. The handle 332 is further formed so that two grooves,grooves 352 and 354, extend outwardly from inner wall of the handle thatdefines bore 350. Groove 352 is proximal to bore 348. Groove 354 isproximal to the distal end of the handle 332. Groove 352 is greater indiameter and length than groove 354.

The handle 332 is formed to have two additional bores, closed end bores356. Bores 356 extend inwardly from the proximally directed face of thehandle 332. Bores 356 are diametrically opposed from each other. Bores356 are parallel to and spaced apart from the adjacent bore 342. Bores356 are dimensioned and positioned so that when the cup remover 30 isattached to driver 50, each driver pin 262 slidably seats in a separateone of the bores 356.

A static head-to-shaft coupler 360, now described by reference to FIGS.32 and 33, is the component that holds cup remover head 388 to thedistal end of shaft 292. Coupler 360 is formed as a single piececomponent. The coupler has a stem 362. In one version of the inventionthe stem 362 has flat parallel side surfaces. Front and rear surfacesthat convex in shape extend between the side surface (individualsurfaces not identified). The stem 362 is formed to define two V-shapedindentations 364 and 366. The indentations 364 and 366 extend inwardlyfrom the opposed front and rear surfaces. The indentation 364 is theproximal of the two indentations. The stem is further formed so that theproximalmost diagonal face that defines indentation 364 is formed tohave a recess 368.

Forward of stem 362, coupler 360 has a cylindrical head 372. Notidentified is the neck with a diameter less than that that of the head372 between the stem 362 and the head. Head 372 is formed withthreading, not identified on the outer circumferential surface.

A closed end bore 378, shown in dashed lines only in FIG. 33, extendsforward from the distal end of stem 362. Bore 378 is dimensioned topress fit receive shaft head 306. A bore 380 extends through the opposedside faces of the stem 362. Bore 380 intersects bore 378. When the cupremover 30 is assembled, shaft head 306 is seated in coupler bore 378. Apin 382, seen only in FIG. 2B, extends through the coaxial head bore 306and coupler bore 380 further holds the coupler 360 to the shaft. Coupler360 is further formed to have a second bore, bore 382, that extendsside-to-side through stem 362. Bore 382 is located proximal to thedistal end of the stem 362.

The pivot head 388, as seen in FIG. 34, has a distal facing surface 390.Surface 390 is designed to be seated in the inner surface of theacetabular cup 32 cup remover 30 is intended to remove. Surface 392 isgenerally in the form of a slice section of a sphere. Pivot head 388 hasa distal facing surface 392 opposite surface 390. Surface 392 isgenerally planner. A ring shaped fitting 394 is mounted to head 388 soas to extend inwardly from surface 390. Fitting 394 defines a close endbore 396. Fitting 394 is formed with threading, not seen, around bore396 so the bore can receive coupler head 372.

Blade 402, now described by reference to FIG. 35, includes a body 404.Specifically in some versions of the invention the body 404 has aproximal section, (not identified). Extending from the proximal sectionthere is a distal section (not identified) that is curved. The bodydistal section is formed with teeth 406.

The blade 402 is further formed to have a tab 408 that extendsperpendicularly away from the proximal section of the body 404. Tab 408is in the form of a rectangular beam. In the depicted version of theinvention, the distal section of the body is formed with an opening 410.An end section of the tab 408 is welded or otherwise secured in theopening 410. Tab 408 is shaped to have a closed end bore 412, (shown inphantom). Bore 412 extends inwardly from the proximally directed surfaceof tab 408.

A hinge 418, seen best in FIGS. 36 and 37, pivotally connects the blade408 to coupler 360. The hinge 418 includes a base 420 that isapproximately rectangular in shape. Base 420 includes top located sidesurfaces that are inwardly tapered toward each other (surfaces notidentified). Two parallel legs 422 project outwardly from one end of thebase 420. Hinge 418 is spaced so that the legs 422 can slip fit over theopposed parallel flat surfaces of the coupler stem 362. Each leg 422 isformed so as to have a rounded free end (not identified).

The hinge 418 is formed that a rectangular slot 426 extends through base420. The longitudinal axis of slot 426 is parallel to the longitudinalaxes of legs 422. Slot 426 is dimensioned to receive the tab 408integral with the blade 402. An opening 428 extends through the topportion of hinge base 418. Opening 428 extends to slot 426. Coaxialopenings 430 (one shown) extend through the opposed sides of the hinge418 where the legs 422 extend from the base 420. Each opening 430partially intersects the base 420. The face of the base adjacent isformed with two grooves 431 (one shown). Each groove 431 has a radius ofcurvature equal to the radius of the openings 430 and has a curve thatis centered on the common axes through openings 430. Each leg 422 isformed with a through hole 423. Leg through holes 423 are coaxial.

The assembly that removably holds blade 402 to hinge 418, seen in FIG.37, includes a sleeve like bushing 432. Bushing 432 is press fit inhinge opening 428. A lock pin 434 is disposed in bushing 432 to move upand down within the bushing. Lock pin 434 has a tip 436 designed to seatin bore 412 integral with blade 402. Above the tip 436 the lock pin 434has a lip 438 that protrudes radially outwardly and circumferentiallyaround the main body of the tip 436. A ring shaped retainer 452 is pressfit into the end of bushing 432 spaced from the hinge 418. Thecomponents are further dimensioned so that the end of the lock pin 434opposite tip 436 protrudes above retainer 452.

A helical spring 450 is disposed around the main body of the lock pin434. Spring 450 extends between the static inner surface of retainer 452and lip 438 integral with the lock pin 434. The spring 450 places aforce on the lock pin 434 that tends to hold the pin tip 436 in hingeslot 426. The end of the pin 434 opposite the tip 436, the section thatextends above retainer 452, is attached to a button 454. In the absenceof another force, spring 450 holds button 454 over bushing 432. Thiscoupling assembly is moved from the run state to the load state bypulling outwardly on button 454. This manual force overcomes the forcespring 450 applies to the pin 434 so as to hold tip 436 in the hingeslot 426.

Upon assembly of the cup remover 30, hinge 418 is positioned so thateach leg through hole 423 is adjacent a separate one of the openingsinto coupler bore 382. A pin 460 extends through hinge holes 423 andcoupler bore 382 to statically hold the hinge 418 to coupler 360.

An actuator rod 468 and an actuator 502 connect the handle 332 to hinge416. Actuator rod 468, now described by reference to FIG. 38, is anelongated solid cylindrical rod. The rod 468 has a diameter thatfacilitates the seating of the rod in shaft groove 302. While rod 468can seat in groove 302, the rod is shorter in length than the groove.Slightly forward of the proximal end, rod 468 is shaped to have a groove470. Groove 470 is concave in shape and extend circumferentially aroundthe rod 468. The actuator rod 468 is further formed to have at thedistal end a head 472. Not identified is the undercut neck between themain body of the rod 468 and head 472.

When cup remover 30 is assembled, the actuator rod 468 is slidablydisposed in shaft groove 302. A lock ring 478, seen best in FIGS. 31 and39, holds the actuator rod 468 to the handle 332. Lock ring 478 isgenerally cylindrical in shape. The lock ring is formed to have aproximally directed head 479. Head 479 has an outer diameter less thanthat of the main body of the lock ring 478. The lock ring 478 is formedto define a bore 480 that is circular in cross section and coaxial withthe proximal-to-distal longitudinal axis through the lock ring,including head 479. Bore 480 is dimensioned to receive shaft 292. Lockring 478 is further shaped to define a groove 482 that extends inwardlyfrom the inner wall of the ring that defines bore 480. Groove 482 isshaped such that when the shaft 292 and rod 468 are seated in the lockring, the portion of the rod 468 that extends above the shaft seats ingroove 482. Groove 482 extends proximally from the distally directedface of the lock ring. The groove 482 does not extend into theproximally located head portions 479 of the ring 478. Thus, a step 483internal to the lock ring defines the proximal end of groove 482.

A bore 484 extends laterally through a portion of the lock ring 478.Here laterally is understood to be in a plane perpendicular to thelongitudinal axis through the lock ring. Bore 484 is located so as tointersect the base of groove 482.

When the cup remover 30 is assembled, shaft 292 seats in bore 480.Actuator rod 468 seats in lock ring groove 482. The proximal end of therod is disposed against step 483 internal to the lock ring 478. Actuatorrod 468 is thus positioned so that the rod groove 470 is in registrationwith lock ring groove 482. A pin 486 seen only in FIG. 2A, extendsthrough lock ring groove 482 and actuator rod groove 470 to hold theactuator rod in a static position relative to the lock ring 478.

Lock ring 478 is rotatably mounted in handle bore 350. Lock ring head479 is disposed in bore 348. A snap ring 488, seen in FIG. 2A, seated inhandle groove 354 holds the lock ring in bore 350. When the cup remover30 is assembled an O-ring 492 is disposed in handle groove 346. TheO-ring 492 is disposed around shaft 292. An O-ring 494 is seated inhandle groove 352. The O-ring 494 is compressed between the handle 332and the outer surface of lock ring 478. The O-rings 492 and 494 functionas seals that minimize the flow of liquids and vapors into the handle332.

Actuator 502, as seen best in FIG. 40, is a single piece unit. Theactuator includes a foot 504. Foot 504 is generally rectangular inshape. The foot 504 is dimensioned to seat on and not extend laterallyoutwardly of shaft flat 304. A leg 506 extends forward from one side ofthe foot 504. The leg 506 is in the form of a rectangular bar. Leg 506has a width less than that of foot. Foot 504 and leg 506 share a singlecommon planar face. A step 508 projects laterally away from the distalend of leg 506. A head 510 extends forward from step 508. Actuator head510 is generally in the form of a right triangle with rounded corners.One of the right angle forming sides of the head is parallel with theproximal-to-distal longitudinal axis along leg 506. The second rightangle forming side of the head is perpendicular to this longitudinalaxis and is immediately adjacent step 508.

A bore 512 seen in phantom extends from the proximal end of actuatorfoot 504. Bore 512 is shaped to receive actuator rod head 472. Theactuator 502 is further formed so as to have a slot 514 in head 510.Slot 514 is located inwardly of the surface of the head that defines thetriangle defined by the head 510. Thus, from the most portion of theslot 514, the slot extends diagonally proximally away and away fromlongitudinal axis of the actuator leg 506.

Actuator 502 is positioned so that foot 504 is disposed over shaft flat304 and leg 506 extends over one of the outer flat side surface ofcoupler 360. The head 472 of actuator rod 468 is threaded in actuatorbore 472, (threading not shown). A pin 516 connects the actuator 502 tohinge 418. Pin 516 extends through slot 514 internal to the actuator andcoaxial openings 430 and groove 431 integral with the hinge 418. Thehead of pin 516 (pin head not identified) is disposed over the outersurface of the portion of the actuator head 510 that defines slot 514.The pin 516 thus performs two functions. The pin 516 connects the hinge418 to the actuator 502. Pin 516 also extends across the rear opening ofhinge slot 426. The pin thus also limits the movement of the blade tab408 in the slot. More particularly, when the blade tab 408 is disposedagainst pin 516, tab bore 412 is positioned to receive lock pin tip 436.

III. Operation

Cup remover 30 of this invention is prepared for use by first fittingthe blade 402 to hinge 418. This is accomplished by pulling up on button454. The manual force on applied to the button overcomes the force ofspring 450 that holds pin tip 436 in hinge slot 426. Once the pin tip isretracted away from the hinge slot 426, blade 402 is mounted to thehinge by seating the blade tab 408 in hinge slot 426. Once the blade tabbore 412 is in registration with the pin 434, button 454 is released.The force spring 450 applied to lock pin 434 hold the pin tip 436 inblade tab bore 412. The blade is thus removably coupled to the hinge414.

The cup remover 30 is then coupled to driver 50. This is accomplished bypulling retainer 236 proximally over the eccentric housing 108. Manualforce is all that is required to overcome the force spring 266 appliesto the retainer 236 so as to hold the retainer away from driver housing52. The longitudinal displacement of the retainer 236 results in theretainer moving so that the bearings 268, instead of being disposed inretainer bore 252, are disposed in retainer bore 256. Bore 256 is largerin diameter than bore 252. The ball bearings 205 are thus free to movelaterally out of the spindle bores 204 and into the annular spacebetween the outer surface of the output spindle and adjacent bore256-defining surface of the retainer. At this time the driver 50 can beconsidered in the state in which the cup remover 30 can be loaded to thedriver.

The cup remover coupling process continues with the fitting of the cupremover 30 so that each one of the pins 262 integral with retainer 236seat in a separate one of the handle bores 356 as seen in FIG. 41. Thecup remover 30 and driver 50 are brought further together so that theinput spindle neck 318 seats in notch 196 integral with output spindle184. This process may require the rotation of the output spindle 184 toplace the neck 318 in alignment with the output spindle notch 196. Oncethe spindles are so positioned, groove 320 integral with the inputspindle 312 is in registration with openings 201 integral with theoutput spindle 184. The force holding the retainer 236 in the loadposition is released. Spring 266 pushes the retainer 236. As aconsequence of this displacement of the retainer, bearings 205 arepressed against the annular wall of the retainer that defines bore 256.The retainer thus pushed the bearings 205 inwardly into the outputspindle bore 204. More specifically, the bearings seat in the groove 320integral with the input spindle 312. The driver 50 is in a state inwhich the cup remover 30 is releasably locked to the driver.

Cup remover 50 is used by positioning the pivot head 388 in the socketof the acetabular cup 32 the remover is being used to remove. Thesurgeon holds the driver handle 62 in one hand and the cup removerhandle 332 in the other hand. Blade 402 is pressed against the boneadjacent the outer surface of cup 32 by pushing the cup remover handledistally, towards pivot head 388. This results in a like movement of theactuator rod 468 and, by extension, actuator 502. The resultant likemovement of pin 516 causes hinge 418 to pivot outwardly. The outwardpivoting of the hinge 418 combined with the curved shape of blade 402forces the blade against the outer surface of the cup 32.

The surgeon oscillates the blade 402 against a section of bone bydepressing trigger 84. This results in the actuation of the motor 68 soas to rotate shaft 70. The rotation of shaft 70 results in the likesimultaneous rotation of the eccentric shafts 136. Specifically, eacheccentric shaft 136 rotates around common access of the shaft foot 138and leg 140. The shaft head 146 rotates around this same axis. Since theshaft head is off axis with this axis, the shaft head 146 is understoodto rotate in a circular motion around this axis. The movement of theshaft heads 146 is captured by the link 168 disposed over the eccentricshaft heads 146. Owing to the arrangement of these components, thismovement results in the link engaging an oscillator rotation around thecommon axis of the link head 176 and nose 178.

The oscillator motion of the link 168 is transferred by the outputspindle 184, the input spindle 312, shaft 292 to link 360. Theoscillation of link 360 results the like oscillation of hinge 418 and,therefore, blade 402 around the axis of shaft 292. Blade 402 is thusoscillated back and forth against the bone the blade is positioned tocut.

In some versions of the invention, blade 402 oscillates over an arcbetween 15 and 2°. In still other versions of the invention, blade 402oscillates over an arc between 8 and 5°.

Once the blade 402 is used to form a cut in some bone, cup remover 30 isdesigned allow the rotation, the indexing, of the blade, so the bladecan remove another section of bone. This step is performed by rotatinghandle 332. The rotation of the handle 332 is, through pins 262,transferred to retainer 236. The rotation of the retainer 236 is,through screws 264, transferred to the eccentric housing 108. Duringthis process it is understood that the eccentric housing base 110rotates against the inner surface of the cup insert main body 93. Owingto the materials from which the cup insert 92 and eccentric housing 108are formed these components are essential their own low frictionbearing. The resultant rotation of the eccentric housing 108 results inthe rotation of the rotational positions of the eccentric shafts 136relative to the motor shaft 70. In other words, the eccentric shafts 136rotate around the fixed axis of the motor shaft 70.

The rotation of the eccentric shafts 136 result in a like rotation ofthe eccentric shaft heads 146. The rotation of the eccentric shaft headscauses the surrounding plates 170 to undergo a like rotation. Thisrotation of the eccentric plates 170 causes the link to rotate aroundthe axis that extends through the link head 176. As described above,rotational movement of the link head 176 results in the same movement ofthe blade 402. Blade 402 is thus rotated to a new rotational positionrelative to a fixed axis that extends from longitudinally along cupremover shaft 292. This axis also extends from driver 50. By againdepressing on the handle 332 and actuating the motor 68, the blade 402can cut the new section of bone against which the base has beenpositioned.

Cup remover 30 of this invention is thus designed so that, once seatedin a cup 32, blade 402 can be rotated a complete 360° to be worked allof the bone against which the cup is embedded. Blade 402 can be sorepositioned without having to shift the position of the driver 50relative to a static axis that extends from the cup. Thus, once thesurgeon establishes a comfortable orientation for holding the driverrelative to the cup 32, there is no need to reorient the driver 50 toensure the blade is cycled completely around the cup.

A further feature of this invention is that the orientation of the blade402 is reset without having to remove and then reinsert the pivot head388 in the cup 32. Thus the effort associated with this indexingoperation does not appreciable add to the overall time required toremove the cup.

IV. Alternative Embodiments

The above is directed to one specific version of the cup remover of thisinvention. Other versions of the cup remover may have features differentfrom what has been described.

For example, in the disclosed version of the invention a number ofcomponents perform multiple functions. There is no requirement that thisfunctionality be present in all versions of the invention. Specifically,the described retainer 236 performs functions associated with: theremovably coupling of the cup remover to the driver; the oscillation ofthe cup remover; and the indexing of the blade. In alternative versionsof the invention the retainer may perform only one or two of thesefunction.

Thus an alternative version of the invention may have a transmissionthat does nothing other than convert the rotational movement of a motorshaft into a motion that oscillates the blade back and forth. A couplingassembly with separate components may removably hold the cup remover tothe transmission. A third unit may perform the indexing function thatrotates the blade around the fixed axis extending from the cup 32. Thisthird unit, the indexing assembly, may be either part of the driver orpart of the cup remover. Alternatively this third unit that performs theindexing, the rotation of the blade 402 around shaft 292 may be separatefrom the coupling assembly and the transmission assembly.

Likewise not all features be present in all versions of the invention.For example, in some versions of the invention, there may not be acoupling unit that removably holds the components distal to the driver50 to the driver. In these versions of the invention, only the blade maybe removably attached to the rest of the invention.

Further, other versions of this invention may include other assemblies.For example, an alternative cup remover of this invention may have twoshafts, for example, an inner and an outer shaft. The inner shaftextends to the pivot head and serves primarily as a support to hold theother components of the cup remover away from the pivot head. The outershaft is rotatably and slidably disposed over the inner shaft. The hingeis pivotally attached to the outer shaft. In these versions of theinvention, the outer shaft is moved longitudinally along the inner shaftto pivot the blade assembly and rotated around the inner shaft to indexthe blade assembly.

In some versions of the invention, additional low friction bearingcomponents may function as the interface between the static cup insert92 and the eccentric housing 108. This “component” may be a lubricant orcoating.

It should likewise be understood that the size and shape of the head 388and the size and shape of the blade 402 are a function of thecharacteristics of the cup 32 that is be removed.

Further there may be versions of the invention configured so thatactuator rod and actuator are likewise able to rotate around the shaft.In these versions of the invention, the rotation of the handle 332 isdirectly transferred from the handle to the actuator rod. The rotationof the actuator rod in turn is applied to the hinge so as to result in alike rotation of the hinge and blade. An advantage of this version ofthe invention is that the transmission components associated with thedrive needed not also be designed to engage in the rotation associatedwith the indexing operation.

In the described version of the invention the driver including thecoupling features integral with the driver 50 to hold the cup remover tothe driver are specifically designed for use with the cup remover. Thismay not be the case with all versions of the invention. It iscontemplated that a cup remover of this invention may be designed towork with a driver that performs other functions. One such driver isdescribed in US Pat. Pub. No. 2007/0021766 A1, SURGICAL HANDPIECE WITHCOMPACT CLUTCH AND ANTI-WOBBLE COUPLING HEAD, the contents of which areincorporated herein by reference. This handpiece, sometimes referred toas a heavy duty driver, includes a rotating spindle. The spindle isshaped to receive surgical instruments in addition to the cup remover ofthis invention. One such instrument is the shaft of a reamer. Anelectric circuit internal to this heavy duty driver is able to oscillatethe spindle. Thus a cup remover of this invention designed to work withthis type of driver may include a coupling assembly designed to hold theshaft to the driver spindle, an assembly for indexing, rotating, theblade around the static axis through the pivot head, and an assembly forpivoting the blade.

Given the above it should be appreciated that some drivers of thisinvention may not rely on a mechanical transmission to convert therotational motion energy of a motor shaft into an oscillatory motion.Other mechanical transmissions such as a transmission that includessingle eccentric shaft be employed. Further, the motor shaft may notrotate. As discussed above, a control circuit may regulate theapplication of energization signals to the motor shaft so that the shaftonly oscillates. In this version of the invention, the transmission maybe a step down assembly that converts 180 to 540° of motor shaftrotation in one phase into 5 to 15° of blade movement.

Further, some cup removers of this invention may have two handles. Thepractitioner manipulates one handle to regulate the pivoting of theblade. The second handle is part of the indexing assembly and ismanipulated to set the rotational orientation of the blade. This twohandle version of the invention may be appropriate so that when thesurgeon moves to pivot the blade the blade is not inadvertently rotated.this design also prevents the surgeon from inadvertently pivoting theblade when all that the surgeon wants to perform is a rotational shift.

The pivot head 388 may be shaped to be received in a liner within a cup32. Some pivots are shaped to be received against the inner surface ofthe cup 32. This inner surface may be the exposed inner surface of theshell once the liner is removed.

Also, while this invention is designed as an acetabular cup remover, theinvention may have other applications. For example after a pilot hole isdrilled in tissue, an alternative version of this invention could beused to form a socket in the tissue.

The invention may have additional applications beyond medicine andsurgery.

Accordingly, it is an object of the appended claims to cover all suchmodifications and variations as come within the true spirit and scope ofthis invention.

What is claimed is:
 1. An acetabular cup remover comprising: a headdimensioned to seat in an acetabular cup; a shaft that extendsproximally from the head; a blade that is pivotally connected to saidshaft, said blade being shaped and being connected to said shaft so asto be selectively pivotable into positions that are located forward ofthe acetabular cup; an actuator assembly moveably mounted to said shaftthat is connected to the blade for controlling the extent to which theblade is pivoted, the actuator assembly including a handle that ismoveably connected to said shaft that is manual displaced to pivot theblade; a coupling assembly for connecting the blade to a driver so thatrotational or oscillatory actuation of a component associated with thedriver is transferred to the blade so as to cause oscillatory motion ofthe blade in arc around the acetabular cup; and an indexing assembly isattached to said blade to cause said blade to, in addition to engagingin both pivotal motion relative to said shaft and oscillatory motion inan arc around the acetabular cup, is able to, upon actuations of theindexing assembly, engage in rotational motion about the axis thatextends along the shaft.
 2. The acetabular cup remover of claim 1,wherein said actuator handle is part of said indexing assembly so thatsaid handle can be manual actuated to both pivot said blade relative tosaid shaft and to rotate said blade around said shaft.
 3. The acetabularcup remover of claim 2, wherein the actuator assembly and said indexingassembly are collectively configured so that: the longitudinaldisplacement of the handle along the shaft results in the selectivepivoting of the blade; and the rotation of the handle results in therotational movement of the blade around the axis along the shaft.
 4. Theacetabular cup remover of claim 1, wherein the handle further includesfeatures for releasably engaging complementary features of the driver.5. The acetabular cup remover of claim 1, wherein: the blade ispivotally attached to the shaft; and said coupling assembly and saidindexing assembly collectively rotatably couple said shaft to saiddriver so that the rotation of said shaft results in a like rotation ofthe blade.
 6. The acetabular cup remover of claim 1, wherein saidindexing assembly includes driver indexing components that are connectedto the driver that are engaged by said coupling assembly so that whensaid driver indexing components are rotated, said coupling assemblytransmits the rotational movement of the driver indexing components tothe blade to rotate the blade.
 7. The acetabular cup remover of claim 6,wherein said indexing assembly includes a handle that is disposed overthe shaft and is connected to said driver indexing components to rotatesaid driver indexing components.
 8. The acetabular cup remover of claim7, wherein the handle that is connected to said driver indexingcomponents is the handle that is part of said actuator assembly so thatsaid handle can be manually manipulated to both pivot the blade androtate the blade.
 9. The acetabular cup remover of claim 6, wherein saiddriver indexing components are further configured to convert therotational motion of the a rotation shaft of the driver into anoscillating motion that oscillates the blade.
 10. The acetabular cupremover of claim 1 wherein: said driver indexing assembly includes: atleast one head that is moveably connected to said driver to, as a resultof the actuation of said driver, said head rotates around an axis thatis laterally spaced from the axis of said head and is connected to saidhead so that the as a result of actuation of said indexing assembly,said head shifts position so that axis around which said head rotateswhen the driver is actuates shifts rotational orientation relative to afixed axis that extends through the driver; and a link that connectssaid head to said shaft so that the rotation of said head when saiddriver is actuated results in the oscillation of said shaft and theshift of head position results in the rotation of said shaft; and saidblade is attached to said shaft to oscillate with said shaft and rotatewith said shaft.
 11. The acetabular cup remover of claim 1, wherein:said blade is pivotally connected to the shaft; said coupling assemblyconnects said shaft to the driver so that oscillatory motion output bythe driver is transferred to the shaft and the blade; and said indexingassembly is configured to rotate said shaft relative to an axis thatextends through the driver.
 12. The acetabular cup remover of claim 11,wherein the handle is connected to said shaft as part of said indexingassembly to rotate said shaft.
 13. The acetabular cup remover of claim11, wherein said actuator assembly is connected to the shaft to rotatewith the shaft.
 14. The acetabular cup remover of claim 1, wherein anactuator rod extends between said handle and said blade to, uponactuation of the handle, pivot the blade.